[PCW] A few things

[Jim Meader]

Will do more searching on controlled pitch props and the forced air hull
cavity concepts.

Thanks for sharing your knowledge and answering my questions so well.

Jim Meader
RE/MAX Today
VM   650-610-6455
Fax   650-591-1043


-----Original Message-----
From: power-catamaran-bounces at lists.samurai.com
[mailto:power-catamaran-bounces at lists.samurai.com] On Behalf Of Malcolm
Tennant
Sent: Tuesday, August 28, 2007 5:07 PM
To: Power Catamaran List
Subject: Re: [PCW] A few things

Jim Meander.

I would like to comment on some of your questions:-

[3] Trash compactors need power to operate them, they aren't cheap [the
probable reason for their absence] and they take up space. We have used
them
on a lot of our designs.

[4] Most propellers are in fact variable pitch, the pitch changes from
the
root to the tip. I presume what you mean is CP [controllable pitch]
propellers. There are dozens of companies manufacturing these and there
are
thousands in use. Several of our designs have used CP propellers.
However
they are very expensive and you have to do big miles to justify their
cost.

[5] All of our designs feature propeller shafts that are parallel to the

waterline and that direct their thrust directly aft. It is one of the
reasons why our CS hull is currently the most efficient around.

[6] It is a good idea but until recently the technology was not
available in
small enough sizes for use in most pleasure boats. Ships, and in
particular,
cruise liners and war ships have used diesel/gas turbine-electric
systems
for decades. There are now a number of manufactures of diesel electric
systems and a large amount of published data and comment. Professional
Boatbuilder magazine has had two articles in its most recent
publications
looking at the pros and cons of such systems and their applications to
pleasure boats.

[7] There are a number of designs, and hundreds of patents, in operation

using exactly what you are proposing. Just the exhaust is not enough so
extra air is required. This takes power and is generally applied to high

speed [planing] craft. There is a system that injects the exhaust into a

cavity above surface piercing propellers so that they are operating
semi-submerged right from the word go.

Regards,

Malcolm Tennant.   ARINA  MA

MALCOLM TENNANT MULTIHULL DESIGN LTD
PO Box 60513, Titirangi.
Waitakere 0642
NEW ZEALAND
Ph: +64 9 817 1988
e-mail: malcolm at tennantdesign.co.nz
www.tennantdesign.co.nz
www.catdesigners.com
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